Automatic telephone system



June 28 1927' R. w. ENGSBERG AUTOMATIC TELEPHONE SYSTEM Filed Angl 1o, 192s Patente-d June 28, 1927.

UNITED STATES PATENT OFFICE.

RALPH W'. ENGSBEEG, OF LAKE MILLS, WISCONSIN, ASSIGNOR, BY MESNE VASSIGrlF- NIENTE, TO AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELAVIARE.

AUTOMATIC TELEPHONE SYSTEM.

Application filed August 10, 1925. Serial No. 49,219.

The present invention relates in general to automatic telephone systems, and more speciiically -to an improved type et secondary rotary line switch to be used with plung er V(Keith) vtype primary line switches for extending calling lines to iirst selectors. In a system o1"l this charac'er the idlel primary line switches ot a group are held poised over the bank springs or an idle 'trunk by a master switch, and when a call is initiated the prin'iary line switch plunges to seize the idle trunk. rlfhe'secondary line switch terminating the seized trunk immediately connects with a selector if its wipers happen to be standing upon the bank contacts ot a trunk terminating in an idle selector; or it its wipers are standing upon the bank contacts of abusy trunk, they are automatically rotated step by step until they tind Aan idle trunk whereupon the rotation is stopped.

rlhe 'foregoing describes the operation ot the known arrangement. This invention, however, provides an improved type of rotary secondary line switch which materially speeds up the service by preselecting action. Y The improved line switch does not preselect at once when released but is caused to preselect by the primary maste1 switch, when the master switch comes to rest onthe particular trunk which extends 4to the secondaryv linel switch in question.

The invention will be more clearlyA understood by reference tov the accompanying drawing, which shows a circuit diagram of the equipment.

Referring to the drawing, the apparatus shown in the circuit diagram may now be briefly described. The substation A is'anj ordinary' automatic .telephone substation having the usual talking instrumentalities and a calling` device for controlling the automatic switches. The line conductors terminate at the exchange in the individual line switch C, which is ot the wellknown plunger type, to be hereinafter explained in detail in connection with its operation.

The master switch'l) is of the type shown and described in Automatic Telephony by Smith and Campbell, second edition, pages ,j 48, 49 and 50, modified however', to include an additional set ci bank contacts and wiper.

The secondary line switch' F is a. non-numerical switch mechanically of the kwell known rotary type in which the wipers have no 'normal position and move'in a forward direction only. Relay 61 is a socalled two step relay. rlhe springs represented by armature 64 and working Contact are closed on the first step, while the springs represented by armature 65 and its contact are not closed until the second step, that is, until the relay is fully energized.`

The irst selector E, shown only in part, is mechanically of th'e usual and well knownV Strowger vertical and rotary type.

Having brieily explained the purpose of the invention and the apparatus involved in carrying it out, the operation ot the equipment may now bey explained more in r detail. `F or this purpose it will be assumed that the subscriber of substation A desires to obtain a connection.

hen the calling subscriber at substation A removes his receiver to initiate thev call, an energizing circuit is completed tor the line relay 14 ot' the line switch which may be traced from ground, right-hand winding of supervisory relay 31 ofthe master switch D, conductor 30, resting contact and spring 20, line conductor 11, over the subscribers loop and return to line conductor'12, resting Contact and spring 2l, and line relay 14 to battery. Upon energizing, line relay 14 closes an energizing circuit at armature 19k for the pull-in winding 18, whichV may be ytra-ced from ground at Vrelay 3,1 and said relay, conductor 30, uf'or'king contact and armature 19, pull-in winding 18, conductor 36, and armature 32 and its resting contact to battery. Pull-in winding` 1t, upon energizing, operates both the plunger varm 15 and the cut-oit armature 16;v the former,

'through thenmc'diuin or its plunger (not shown), forces the bank springs 24-26, in-

clusive. int-o cngagcn'ient, respectively, with the contacts 2729, inclusive, vand the latter disconnects the line conductors y12l and 11 from the line relay .14 and from ground, `respectively. By the engagement of bank springs 24426, inclusive, with contacts 27-29, inclusive,the line and holding conductors are extended to the secondary 'line switch F.

By the extension of the' line conductors at banksprings 24 and 26 and contacts 27 and 20acircuit is closed for the line relayr G1 of secondary line switch F as `follows:

ground, resting contact and armature 78, bank Contact 29, bank spring 26, line conductor 11, over the subscribers loop and return to line conductor 12, bank spring 2st, bank contact 27, armature 66 and its resting contact, and relay 61 to battery. Relay 61 is a socalled two step relay and is already partially energized under control of the master switch to hold armature 6a attracted. 'l`his relay now 'fully energizes and attracts armature 65, which closes a circuit by way ot bank contact 28 and spring 25 tor the hold winding 17 ot' the primary line switch C, and places ground potential by way et conductor 13 on the multiple test conta-cts in the banks or connector switches having access to the line ol substation A, whereby said line is made busy. Line relay 11i is made slow-acting and holdsthe circuit oft pull-in winding 18 closed until ground potential is returned by the secondary line switch F Ator hold-winding 17, which winding is insuiticient to operate the plunger arm, but is suliicient to hold said arm after it has operated.

As a further result ci" the attraction ot armature of the secondary line switch l?, a circuit is closed through the master switcl l), whereby said switch is operated in the wellL known manner to advance theiiully restored plungers or the ren'iaining idle line switches into position before the terminals of the next idle trunk line. During the operation ot the master switch the circuit including the pull-in windings such as 18 is opened at armature 32 to prevent the plunging of a line switch during rotation.

As a still further result of the attraction of armature 65, it closes a circuit for relay 62 in series with rotary magnet 623, the latter not energizing in this circuit due to the high resistance of the former. Relay 62, upon energizing, disconnects the relay 61 from the master switch D at armature 68; disconnects the rotary magnet 63 from the selector E at armature 67; and at armatures 66 and 7 3, disconnects the trunk conductors from the relay 61 and ground and extends them to the wipers 70 and 72, respectively, thus closing a circuit t'or the line relay 8O ot the selector E which may be traced as follows: ground, lower winding oit' line relay 80, resting contact and armature 84, bank Contact 76, wiper 72, working contact and armature contact and armature 7 3, bank contact 29, bank spring 26, line conductor 11, over the subscribers loop and return to line conductor 12, bank spring 24, bank contact 27, armature 66 and its working contact, wiper 70, bank contact 741-, armature 83 and its resting contact, and upper winding of relay 8O to battery. Relay 80, upon energizing, closes a circuit for release relay 81, which energizes to connect ground to the release trunk conductor at armature 82 to hold the preceding switches in operated condition. The relay 61 being slow to release, holds up until this ground potential is returned by the selector E.

The calling subscriber may now operate his calling device in accordance with the lirst digit of the called number, and the selector E will raise its wipers to the correct level and rotate in to select anidle trunk leading to a succeeding switch, whereupon its switching relay will operate to extend the connection. Ground potential is returned from the last seized switch, up to and inclufiling the connector, over the holding conductor to hold the preceding switches; all of which is in the usual well known manner. rlhe connector tests the called line and it round busy it denies the connection and gives a busy tone to the call-- ing subscriber who restores his receiver. It, however, the called line is found idle the connector completes the connection and rings the called partys bell. The called party, upon answering, by lifting his receiver, stops the ringing and completes the talking circuit, whereupon the subscribers may converse as desired.

lie calling subscriber will linally terminate the conversation, and will replace his receiver, bringing about the disconnection ot the apparatus in the usual manner. Brieiiy, upon the deenergization of the line relay at the connector (not shown), its release relay deenergizes and breaks the holding circuit of the preceding switches, whereby all the switches including' the selector E, secondary line switch F, and primary line switch G are restored to normal position. llfhen relay 62 ot the line switch F falls back and armature 68 engages its resting contact, relay 61 is not energized because wiper Se ot' the primary `master switch has passed oil troni contacti.

Eventually the'inaster switch will again come to restwith its wipers as shown and llt) a circuit Ais closed for the two-step relay 61 which may be traced i'rom grounded sliding contact 35, wiper '34, contact 33, resist-ance resting contact and armature 66, andV relay 61 to battery. Relay 61 only energizespartially in series with resistance 69 to operate armature 6a and prepare acircuit tor the stepping magnet 63. It the trunk upon which the secondary line switch is resting is bus O'round aotential will be resent onY the release trunk conductor and a circuit may be traced from ground, armature 82 and its working contact or selector E, contact 75, wiper 71, armature 67 and its resting contact, working contact and armature64l, and stepping magnet 63 to battery. Stepping niagnet 63 will energizeover this circuit and operate to step the secondary line switch to the next succeeding trunk, etc., until an idle trunk is found, whereupon the idle trunk is preselected by the secondary line switch under controll of the master switch.

Having described my invention, what .l consider to be new and desire to have protected by Letters Patent will be pointed out in the appended claims.

iVhat is claimed is: l

In a telephone system, a non-numerical switch having wipers which normally stand on the trunk line last used, a plunger line switch controlled over a calling subscribers line for seizing said non-iiuiiierical switch, a master switch t'or positioning said line switch before said non-numerical swit-ch, and means responsive to the operation ot said master switchtor causing said non-V nunierical switch to seek an idle trunk line.

in an ,automatic telephone system, a non-numerical switch, trunk lines accessible thereto terminating in contacts, means for making certain ot said trunks busy, wipers for said switch normally standing on the contacts of one ot' said trunk lines, a relay in said switch operable in two stages, a motor magnet for said switch, means Jfor holding said relay operated in the tirst stage as long as said switch is in seizable position and yet unseized, and means controlled by the operation ot said relay in said iirst stage forcausing the operation of said kmotor magnet to move said wipers into engagement with the contacts of an idle trunk line.

ln' an automat-ic telephone system, a non-numerical switch, trunk lines accessible thereto terminating in contacts, means for making certain ot' said trunks busy, wipers i'ior said switch normally standing on the contacts of one of said trunk lines, a lrelay in said switch operable ,in` two stages, av

motor magnet for said switch, means for holding said relay operated in the lirst stage long as said switch is in seizable position `primary plunger line switches each -individual to a subscribers line,`ot a plurality otl secondary rotary line switches accessible to said primary switches, a group ot' trunk lines accessible to said secondary switches, a n aster switch operated responsive to the seizure ot one of said secondary switches for positioning the idle primary switches before an idle secondary switch and means effective when idle primary switches are placed opposite an idle secondary switch for causing said idle secondary switch to hunt for an idle trunk.

5.' In a telephone system, a primary line switch, a plurality of secondary` line switches, a plurality of trunks accessible by way ot' said primary switch and one ot' said secondary switches connected in series, -a master switch arranged to prcselect the secondary y switch next to be used, means operated responsive to the selection ot the secondary switch for selecting an idle trunk, a relayrin the secondary switch operate-d responsive to the operation of the primary line switch, means controlled by said relay for seizing the selected trunk, means for operating the master switch to select a different secondary switch for subsequent use responsive to the operation ot said relay, and means responsive to the seizure of the trunk to release said relay. i Y 6. In a telephone system, the combination with a plurality of primary line switches, of aplurality ot' secondary line switches accessible to each ofthe p 1imary line switches, a plurality ot' trunks accessible to each secondary line switch, a master switch t'or preselecting an idle secondary switch, a relay inv each secondary switch operated responsive to the selection ofthe switch to cause the switch to hunt for an idle trunk, meansA for seizing theI idle trunk, and connections controlled by said last named means for releasingthel li'rst named relay.

f7. AIn la telephone system, a primary line switch, a plurality of secondary line switches, Y

,idle trunk, means for taking the secondary line switch into use, said lirst named means being'con'trolled by the master switch be-l fore the secondary switch is taken into use and over the talkingconductors it' when the secondary line switch is taken into use trunk has not yet been found.

8. In a telephone system, a primary line i,

switch, a plurality 'of secondary line switches, a master switch for associating the Yprimary line switch with an idle secondary line switch, a plurality ot trunks accessibleto the secondary line switch, means in the secondary line switch operated over either of two paths one of which is effective when the switch is preselected bythe master switch andthe other when the switch is taken into use,l and means controlled by said rst named means tor operating the secondary line switch to select an idle trunk. 9. In' an automatic telephone system, a'

I plurality of subscribers lines, a plurality of primary line switches one 'for each line, a plurality or secondary line switches accessible to each primary line switch, each secondary line switch having a plurality of trunks accessible thereto, a master switch arranged to preseiect an idle secondary switch, means in each secondary switch operated only when the. swi 'ch is preselected to select an idle triink, and means operated responsive to the operation ot' the prii'nary line switch to indicate a busy condition oi' the calling line.

l0. In an automatic telephone system, a subscribers line, a primary line switch.y a plurality olf secondaiy line switches, a plus rulity ot trunks acc ssible t the line by way t said primary switch and a scondary swi ch connected in series, an automatic swim tei 'iinatingv euch trunk, a master switch arranged to preselect the secondary switch nest to he used, means operated r sponsive to the selection cii the secondary switch to select an idle trunk, means operated responsive to the initiation ot a call to seize the preselected secoi'idary line switch and the preso k,sled idle trunk, nuans at the aiitomatic switch operated when the switch is scizal to indicate a busy condition of the automatic switch and et the secondary line switch. v

ll. ln an automatic telephone system, a suhscrihci"s line, means for extending callingconnections to the line, means including a primary line switch, a plurality of secondary line switches accessible thereto, and a plu ality ot directively operated automatic g connections to the line', means including,` a

primary line switch7 a plurality ci secondary line switches accessible thereto7 andL a plurality of directively operated auton'iatic switches accessible to the secondary lineswitch for extending calling connections from the line7 master switch tot' proselecting an idle secondary line switch Jr'orl sul'isequent use7 means in the secondary line switch ope- Y ated responsive to its selection to select. an idle automatic switch7 means iu the sec onilary line switch operatedv responsive lo the initiation of a call over the line to prevent the establishment of callinlor connections to the line to seize the automatic switch, and to ope ate the master s itch to select a dif- Yi'erent secondary line switch for subsequent use, and means at the subscribers line for directively operating the seized automatic switch.

In witness wnereo'l, l hereunto subscribe my name this 3rd day ot August, A. D., H525. l

RALPH W. ENGSBERG. 

